Using automatic code differentiation in power flow algorithms

First order derivative computations (Jacobian matrices) are required by power flow studies. In this paper the computation of the sparse Jacobian matrix is implemented using an automatic code differentiation tool for FORTRAN77 code. The user only programs the code for the computation of the numeric mismatch values of all equations. The automatic generation of the derivative code includes also the automatic consideration of inherent sparsity of the Jacobian of the power flow equations. This approach allows the coding as explicit equations of also complex features such as remote voltage and area interchange control, controlled quantity limits and the dynamic change from one equation set to another during the power flow iterations. The resulting power flow code is easy to enhance and to maintain, shows good execution speed and has been successfully applied to network systems as large as 2550 nodes.